1. Field of the Invention
This invention relates to a method for producing biofuels. In one aspect, this invention relates to a method for producing biofuels from biomass. In another aspect, this invention relates to the production of biofuels using the NEMCA effect, i.e. non-Faradaic electrochemical modification of catalytic activity, also known as electrochemical promotion of catalysis (EPOC).
2. Description of Related Art
The principal methods for producing chemicals from biomass are biomass refining or pretreatment, thermo-chemical conversion (gasification, pyrolysis, hydro-thermal-upgrading (HTU)), fermentation and bioconversion, and product separation and upgrading. There are five main categories of building blocks that can be identified as intermediates for the production of chemical products from biomass:                1) Refined biomass, i.e. biomass from which the valuable components, having been made accessible by physical and/or mild thermo-chemical treatment, are extracted after which the remaining biomass undergoes further transformation;        2) Biosyngas, primarily CO and H2, which is a multifunctional intermediate for the production of materials, chemicals, transportation fuels, power and/or heat from biomass and which can easily be used in existing industrial infrastructures as a substitute for conventional fossil-based fuels and raw materials;        3) Mixed sugars, C5 and C6 sugars, which are further refined substrates for chemical and bioconversion and which mainly originate from side streams in the food industry and potentially from ligno-cellulosic biomass streams;        4) Pyrolysis oil, i.e. oil produced in fast and flash pyrolysis processes which can be used for indirect co-firing for power production in conventional power plants, for direct decentral heating purposes, and potentially as high energy density (important in case of long distance transportation) bio-based intermediates for the final production of chemicals and/or transportation fuels; and        5) Biocrude, i.e. fossil oil-like mixture of hydrocarbons with low oxygen content, which results from severe hydro-thermal-upgrading of relatively wet biomass and which potentially can, like its petroleum analog, be used for the production of materials, chemicals, transportation fuels, power, and/or heat.        
Refined biomass comprises primarily mixed sugars, fatty acids, or syngas. The transformation of refined biomass into a variety of chemical products, such as fuels, is a very complicated process due to the importance of separation technology in providing an efficient and cost effective biocatalytic production process. Different refined biomasses require different treatments to become useful products. For example, fatty oil is processed through a transesterification reaction to produce useful biodiesel fuel. In this case, KOH is used as a catalyst while fats and oil react with methanol. However, the complicated process involves complicated separation paths and is apparently neither effective nor efficient.
The NEMCA effect is based on the discovery that by applying an electric voltage between, on the one hand, an active material which is applied, preferably in the form of layers, to a solid electrolyte and, on the other hand, a further metallic substrate, also preferably in the form of layers, which is in turn connected to the solid electrolyte, it is possible for the activity or selectivity of a catalyst to be greatly altered. More particularly, it has been found that when using an O2−, H+, or other ion conducting solid electrolyte in a catalytic electrochemical device, the catalytic reaction rate is significantly greater (on the order of 105 times greater) than the Faradaic rate. These phenomena have been observed, for example, in the hydrogenation of unsaturated organic compounds. See U.S. Pat. No. 6,194,623, which teaches a process for the selective hydrogenation of at least one organic compound having at least one unsaturated group, using the NEMCA effect, wherein the at least one organic compound having at least one unsaturated group is a hydrocarbon having C—C double bonding or at least one C—C triple bond, or a mixture of at least one hydrocarbon having at least one C—C double bond and at least one hydrocarbon having at least one C—C triple bond. The at least one organic compound is brought into contact with a hydrogen-containing gas in the presence of a catalyst, wherein the catalyst comprises an active material which is applied to a solid electrolyte to which, in turn, a metallic substrate is connected in such a way that a current flows through the solid electrolyte, so that the active material can be kept at a constant potential and a voltage is applied to the catalyst during the hydrogenation. More than 70 different catalytic reactions (oxidations, hydrogenations, dehydrogenations, isomerizations, decompositions) have been electrochemically promoted on Pt, Pd, Rh, Ag, Au, Ni, IrO2, and RuO2 catalysts. The solid electrolytes are O2− conductors, such as Y2O3 stabilized ZrO2 (YSZ), H+ conductors, such as CaZr0.9In0.1O3-α and NAFION®, F− conductor (CaF2), and the like. However, no incremental chain increases have been found to occur.
Deoxygenation and decarboxylation are rarely reported at high temperatures with big molecules, for example, chains with more than five carbons. However, in the liquid phase, decarboxylation has been reported. See, for example, U.S. Pat. No. 6,238,543, which teaches a process for electrolytic coupling of carboxylic acids carried out in a polymer electrolyte membrane reactor in which gaseous or neat (i.e. without water) liquid reactants are used without the use of organic co-solvents while preventing the loss of platinum and permitting the use of oxygen reduction to water as the cathode reaction. In this case, the use of a neat organic acid is necessary to prevent oxygen production at the anode electrode. Consequently, the method disclosed therein, which is necessarily carried out at temperatures less than 120° C. due, among other things, to limitations of the NAFION electrolyte employed therein and which requires cell potentials of at least about 3.0 volts, cannot be used for bio-oil treatment due to the presence of about 17% by weight water therein.